Electrical insulation



March 24, 1942. H. HIWERMINE ELECTRICAL INSULATION Filed Feb. a, 1940 2 sheets-sheet 1' Mlch 24, 1942 l L H. H. WERMINE 2,277,178

ELECTRICAL INSULATION Filed Feb. 8, 1940 2 SheebS-Sheell 2 J2/HKM;

Patented 51u24, 1942y UNITED lSTATI-:s PATENT-OFFICE 2,211,178

anacrmcar. mspLfrroN Hugo HfWerminc, Wheaton, lll., assignor to Belden Manufacturing Company, Chicago, lll.,

a corporation of VIllinois Application February 8, 1940, Serial No. 317,922

7 claims.

My invention relates to electrical insulation, and particularly to hollow sheath insulation products of the general type known as spaghetti.

Substantially all of the spaghetti type insulation used at the present time constitutes a ilexlble, tubular body or sheath, usually of woven fabric, which is impregnated with an insulating lacquer or varnish. vThe product is put into use by slipping a suitable length thereof over the conductor or wire which it is desired to insulate.

Large quantities of spaghetti type insulation are used annually in the radio, telephone, and other electrical industries, yet the product is relatively expensive, due at least in part' to the almost insurmountable dimculties encountered when an attempt is made to manufacture this insulation by a continuous process. In fact these diiilculties are so troublesome that practically all spaghetti type insulation is manufactured on metal mandrels in relatively short lengths, the mandrels being withdrawn immediately following the forming operation and the product being handled and shipped in short, straight lengths. In addition to the resulting excessive cost of the product, some diillculty has been experienced in storing, transporting, and using insulation of this type because of its lack of internal Support and resultant tendency to collapse.

lThe principal object of the present invention, thereforel is to provide an improved hollowsleeve or spaghetti type insulation, which can be manufactured at low cost by a continuous manufacturing process. Other objects of the invention are to provide an improved spaghetti type insulation which can be wound onto reels in relatively long lengths without collapsing or injury, thereby facilitating the storage and transportation of the product and at the same time eliminating the Waste incident to the use 40 tutes a continuous cylindrical cord which may be of the short length prior art products; to provide an improved method of manufacturing hollow-sleeve type insulation such as spaghetti at low cost; and generally to provide an improved hollow-sleeve type insulating product.

The foregoing and other objects and the various novel features and advantages of the improved product of the present invention will be made lmore apparent by reference to the following description and accompanying drawings of 50,

one preferred -embodiment thereof. In the drawings:

Figures l, 2, and- 3 are perswtive views illus-- trating three steps oi one method oi' manufac- (Cl. 13S-55) present. invention, a completed embodiment of the invention being illustrated in Figure 3;

Figure 4 is a perspective view illustrating the general manner in which the product of the present invention is prepared for use; o Figure 5 is a perspective view, partially in section, showing the embodiment of the invention illustrated in Figure 3 ready for use Figure 6 is a fragmentary view, partially in section, illustrating one use of the product of the present invention; and y Figures 7 throughl l2 are perspective views, generally similar to Figures 3 and 5, illustrating various other embodiments of the insulating product vof the present invention.

The product of the present invention ismanufactured as a continuous cord, and will ordinarily comprise a flexible, tubular sheath of insulating material disposed about a cord-like,-

exible core which is capable of being withdrawn from within the sheath in substantial lengths so as to produce a yhollow insulation. Preferably, the sheath will include a plurality of layers, at least one of which is of fabric, paper, or

similar material.

In the particular embodiment of the invention j lillustrated in Figures 3 and 5, the insulating sheath is of two-layer construction. The inner layer in this form is the reinforcing layer. and comprises a hollow, flexible, woven fabric tube Il; the outer layer comprises a=coating of lacquer or varnish which preferably impregnates the inner fabric layer ll. The core l5 constiformed by twisting together a plurality of sheets in Figure 1.

During the manufacture of the product illustrated in Figures 3 'and 5 it is contemplated that the core l5 shall be used as a form Aor mandrel and that the inner fabric tube il shall be formed thereupon byma weaving operation such as braiding or knitting. The lacquer or varnish layer I3 will then be applied directly to the fabric sheath I l while it is in place on the core i5.

The embodiment of the invention illustrated in Figures 7 and 8 differs from the embodiment of the invention just described, in that the insuturing the improved insulation product of the lating sheath which overlies the core consists of a plurality of layers of similar material, preferably an insulating lacquer or varnish. The core I9 utilized in this form of the invention preferably comprises a cylindrical cord of suitable material similar to the core I5, and the insulating sheath is formed on the core I9 by a dipping or spraying operation, the effect of which is to apply a plurality of superimposed, thin, tubular layers 2l of lacquer to the core Iias illustrated in Figure 7. f

. The successive lacquer coatings or layers 2| may conveniently be applied byv apparatus similar to that used for applying enamel or lacquer coatings to wire. The use of a plurality of thin lacquer coatings serves to produce a sheath'of` very considerable mechanical strength and or very uniform dimensions. In fact, the mechanical strength of this sheath, apparently as a result of its laminated construction, is sufdcient to make possible, in many instances, the elimination of the mechanical reinforcing layer which is used in the other forms of the invention. 'I'he multi-layer form of Figures 7 and 8 has a further advantage in that it may be produced in almost any conceivable color, through the addition of suitable pigment to one or'more of the lacquer coats. The principal advantage of this form, however, is its remarkably low cost and extremely high insulating ability, both of which result from the use of lacquer alone in the formation of the constituent multilayers of the sheath. In certain instancea'it may be desirable to uti lize a mechanical reinforcing layer in connection with the multi-layer form of the invention illustrated in Figures 7 and 8. 'This reinforced type.

rwhich is illustrated in Figures -9 and 10, is particularly suitable for insulating sleeves of fairly large cross-sectional area.. The core 23 utilized in this form of the invention is a cylindrical cord of the same character as the core f previously describedn The first step in the manufacture of this form of the invention will usually consist in the application of the reinforcing layer to the lcore 23 as illustrated at 25 in Figure 9, although if desired one or more lacquer layers 2l may be applied to the core 23 before the reinforcing layer is applied. 4The reinforcing layer may be of any convenient type and may consist of a paper or fabric tape wrapping as illustrated at 25 in Figures 9 and 10, a woven sleeve as illustrated at il in Figures 3 and 5, or a thread wrapping or serving as illustrated at 3i in Figures 11 and 12.

Experiments have shown that a reinforcing layerJ which consists of a tape or thread wrapping,es peeially when that wrapping is impregnated with lacquer, is about as satisfactory as a layer of the woven type. After the reinforcing layer 25 is iny trated in Figures 11 and 12, a tape wrapping as illustrated in Figures 9 and 10, or a woven sleeve as illustrated in Figures 3 and 5, and an outer insulating layer 33 of rubber compound or similar material which is preferably extruded onto the core with the inner reinforcing layer` 3l in place thereon. It is desirable but not absolutely essential that a good bond be obtained between the inner reinforcing layer and the outer insulating layer. 'I'he extruded form of the invention, like the embodiment illustrated in Figures '7 and 8, lends itself particularly well to quantity production, and hence may be manufactured at a very low cost. The extruded sleeve form will not yield'an insulation of as uniform thickness as the sheaths of the previously described embodiment, and being of rubber or rubber compound or similar extrudable material, may not be suitable for all instances. It is possible to manufacture the extruded form without the use of a reinforcing layer, particularly when the physical strength of the product is not of prime 'to leave the sheath in the form of a hollow, tu-v bular insulation, as illustrated in Figures 5, 8, 10, and 12.l The hollow insulation may then be slipped over a wire or conductor 35 which it is 'desired to insulate. as illustrated at 31 in Figure 6.

Various flexible materials, such as multistrand or single-strand paper or-flber cordage, may be used for the removable core portion of the product. However, since the primary functions of the core are to provide a form for the manufacture of the insulating sheath and to provide a removable internal support for renderplace, a plurality of thin, lacquer coatings or layers 21 are applied by a dipping or spraying operation, similarly to the coating layers 2i of the multiple-layer embodiment of Figures 'l and 8. The reinforced multi-layer form of the invention illustrated in Figures 9 and 10 is characterized by very great physical strength accompanied by excellent insulating ability. Both characteristics result from the combination of the reinforcing layer with a plurality of lacquer layers which may be made sufficiently thick to yield almost any desired insulation resistance.

One other form of the invention is illustrated in Figures 11 and l2. This embodiment includes a cylindrical, cord-like core 29 similar to the cores used in the other forms of the invention, an inner mechanical reinforcing layer 3l which may comprise a thread or cord wrapping as illusing the sheath self-sustaining prior to its use, the material from which the core is made should be relatively inexpensive. To assure easy withdrawal of the core from within the sheath, the core should be sufficiently hard to resist compression during the sheath forming operation, although waxing or twisting the constituent strands of the core will also facilitate separation of the core and sheath and will permit the use of fairly soft cores. For maximum convenience in the manufacture and use of the product, it is veryv desirable that the core shall be flexible.

The twisted paper cord illustrated in Figure l has proven a very satisfactory core material and its use is particularly recommended.

. As indicated in the foregoing, the preferred form of the present invention includes a mechanical reinforcing layer and at least an outer layer of insulating material, althoughy it is possible, as in the case of the multi-layer form of the invention .illustrated in Figures 7 and 8, to utilize a number of layers of a single material, and in the extruded form of Figures 11 and l2 it is sometimes possible, especially when a thin wall is used, to eliminate the reinforcing layer altogether. The provision of an insulating layer inside the mechanical reinforcing layer. as illustrated in Figures 9 and 10,.is optional.

Various fibrous materials` capable of being formed into threads, tape or other fabric, as for example linen, cotton, silk, asbestos, glass, cellulose flber, etc., may be used for the mechanical reinforcing layer. Most frequently, this layer will constitute a woven or braided sleeve, as illustrated in Figure 3, or a simple wrapping, as illustrated in Figures 9 and 11, and either thread or tape may be used with very good success. For this reason the terms reinforcing layer and fabric sheath, as used herein, are intended to cover reinforcing layers and sheaths of any of 'the foregoing types of materials, whether applied by weaving, knitting, .braiding or wrap- .ping, and whether in the form of thread, tape,

fabric, or otherwise.

Most of the insulating lacquers and varnishesand similar materials now in use for insulation purposes will be found satisfactory for use in manufacturing the insulation of the present invention. For this reason, the term lacquer, as used herein, is intended to include insulating lacquers and varnishes ofthe ordinary types, cellulose derivatives such as ethyl cellulose and cellulose acetate', and various other similar materials which are suitable for use as an insulating varnish or insulation impregnating material.

From the foregoing it will be seen that I have provided an improved continuous cord insulation product which can readily be converted into hollow insulation similar to spaghetti type insulation. The product of the present invention can be readily manufactured at high speed and without the use of any special equipment. When completed the product is self-sustaining due to the presence of the removable core, and it may be wound onto spools or reels for convenient storage and transportation. The product is at all times ready for use, and waste is entirely eliminated due to the fact that the forming and supporting core may be readily withdrawn from any reasonable length of the insulation sheath. Actual manufacturing experience has shown that the product of the present invention can' be manufactured much more rapidly and at much lower cost than any of the comparable productsheretofore used in the art, and more than this, the product of the present invention is more uniform and more easily handled than the prior art products. i

It will be apparent to those skilled in the art that various modified forms of the present invention may be developed. Accordingly, it is my desire that the accompanying claims Vshall -low insulation.

tioned about said core, said core supporting said sheath so as to prevent crushing or collapse thereof when said cord is wound onto a reel, and means for preventing a, bond between said sheath and said core whereby said core shall be capable of being withdrawn from within said sheath ln substantial lengths to provide a hollow insulation.

3. A continuous cord comprising a solid, continuous, substantially cylindrical, flexible core of disposable fibrous material, a tubular sheath which comprises a plurality of layers of insulating material positioned about said core, said core supporting said sheath so as to prevent crushing or collapse thereof when' said cord is wound onto a reel, and meansfor preventing a bond between said sheath and said core whereby said core shall be capable of being withdrawn from within said sheath in substantial lengths 4. A continuous cord comprising a solid, continuous, substantially cylindrical, flexible, disposable core of fibrous construction and a flexible, tubular sheath which consists of a plurality of layers of insulating material and a mechanically reinforcing layer positioned about said core, said core supporting said sheath so as to prevent crushing or collapse thereof when said cord is wound onto a reel and said core being capable of being withdrawn from said sheath in substantial lengths to provide a flexible, tubular insulay tion.

be accorded the broadest reasonable construci tion consistent withthe language appearing therein and the prior art.

I claim the following as my invention:

1. A continuous cord comprising a solid, continuous, flexible core of disposable, twisted paper construction and a tubular sheath of insulating material positioned about said core, said cre supporting the said sheath so as to preventcrushing or collapse thereof when said cord is wound onto a reel, and said core being capable of being withdrawn from said sheath in substantial lengths to provide a iiexible, tubular insulation.

2. A continuous cord comprising a solid, continuous, flexible core of disposable, twisted paper construction, a tubular sheath which comprises a plurality of layers of insulating material -posi- 5. A continuous cord comprising a solid, con- -tinuous, substantially cylindrical, fiexible core of twisted paper constructiom'a tubular sheath which consists of a plurality of layers of insulating material and a mechanically reinforcing layer positioned about said core, said core supporting said sheath so as to prevent crushing or collapse thereof when said cord is wound onto a reel, and means for preventing a bond between said sheath and said core whereby said core shall be capable of being withdrawn from within said sheath in substantial lengths to provide a hollow insulation.

6. A continuous cord comprising a solid, continuous, substantially cylindrical, exible, disposable core of fibrous material, a flexible, tubular, fabric sheath overlying said core, said sheath being impregnated with an insulating lacquer, said core supporting said sheath'so as to prevent crushing or collapse thereof when said cord is wound onto a reel, and means for preventing a bond between said sheath and said core whereby said core shall be capable of being withdrawn from within said sheath in substantial lengths to provide a hollow insulation.

7. 'A continuous cord comprising a, solid, continuous, flexible, disposable core of fibrous material and a tubularv sheath which consists of av plurality of superimposed layers of insulating lacquer positioned about said core, said core supporting said sheath so as to prevent crushing or collapse. thereof when said cord is wound onto. a reel, and said core being capable of being withdrawn from said sheath in substantial lengths to provide a flexible, tubular insulation.

\ HUGO H. Ward/HNE.l

to provide a hol. 

